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    SubjectRe: Handling interrupts from userspace
    > On Thu, 29 Jul 1999, Alan Cox wrote:
    > > The kernel has to clear the IRQ cause on PCI or Nubus which means it has
    > > to know about the card. Writing a small card specific driver to send
    > > a signal each irq and clear the irq in kernel space works
    > The interrupt handler can also disable the IRQ in the PIC. This
    > will prevent further interrupts after exiting the handler.

    It doesnt work for PCI for all cases

    > 2) you do a read() on the device. This enables the interrupt in the
    > PIC and blocks the process until an interrupt occurs. Then the
    > interrupt is disabled again (in the PIC) and the read() returns 0.
    > 3) you clear the IRQ on the card.
    > 4) goto 2) if you want.
    > When you close the device, the interrupt is freed.

    The card is on IRQ 9 you disable IRQ 9 you return to user space. IRQ 9 is shared with the
    disk. You do a disk I/O. Goodbye computer

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